The present invention relates generally to the design, manufacture and use of blow molded polyester bottles and similar containers having sufficient dimensional stability to permit hot filling of the container.
Certain commodities require or at least are preferentially bottled at temperatures well above room temperature, often above about 170.degree. F. (about 75.degree. C.). Containers made of polyesters, such as polyethylene terephthalate, have typically required certain designs and treatment in order to retain their dimensional stability under such filling conditions. Absent the required design and treatment, polyester containers filled with a hot liquid can often exhibit significant shrinking and other deformation which can prevent the container from accepting a closure to seal the container and can exhibit other deformation which inhibits the commercial acceptance of the container.
When a container is hot filled and sealed at the hot fill temperature with an appropriate closure, the subsequent cooling of the filling material causes that material to contract thereby occupying less volume within the container. As a result, most prior designs for polyester containers adapted for hot filling have employed special panels and other features, typically situated in the sidewall of the container, to permit portions of the container to collapse inwardly in response to the temperature dependent contraction of the material within the container. Examples of such containers are shown in U.S. Pat. Nos. 4,822,543 and 4,863,046. Other containers have been designed which avoid the use of such collapse panels, but which incorporate concentric bands of varying thermally induced crystallization together with certain reinforcing features to reduce the overall flexibility of the container wall. An example of such a container is disclosed in U.S. Pat. No. 4,618,515. Such banded containers generally require significantly greater amounts of resin in order to provide the wall strength necessary to prevent collapse under the heat shrinkage of the container contents.
In copending U.S. patent application 07/696,831, it is proposed to form a container adapted for hot filling which includes a thin flexible side wall that avoids the use of collapse panels. In order to achieve the manufacture of such a container, certain modifications in the structure and process employed in blowing molds were adopted. Further, changes in packaging procedures were made in order to accommodate the new container. While the container disclosed in that application performed satisfactorily and in the intended manner, the rather small foot print of the container made it somewhat unstable. Additionally, further reductions in the amount of resin employed to form the container were desired.
Designs for larger foot print containers of one piece design have been developed recently for use in cold bottling principally of carbonated beverages. Examples of such containers are to be found in U.S. Pat. Nos. 4,865,206 and 4,978,015 as well as PCT publication WO 86/05462. A further example is to be found in copending U.S. patent application 07/592,778 now U.S. Pat. No. 5,024,340. Such containers are generally not suitable for hot filling due to their lack of dimensional stability discussed previously. In accordance with the present invention, it is proposed to construct a container suitable for hot filling which utilizes some of the design criteria previously employed in connection with such one piece wide foot print containers.